Mobile devices are popular due to their inherent portability and multi-functionality. Mobile devices offer a user a variety of functions such as a communication function, a still camera or video camera function, a broadcast receiver function, an Internet access function, and the like.
Meanwhile, some mobile devices provide a search function. Typically the mobile device provides a search function using a file name. However, such a typical search technique has a drawback in that it is difficult to obtain desired results according to types of file name. For example, if a photo file is not named by a user, but automatically named by the system (e.g., as a corresponding date or a predefined expression with increasing numbers), it is very difficult for a user to find a desired photo file.
Recently another search technique using metadata of files has been proposed. However, metadata has only information produced by the system such as a file size, resolution, shooting time, weather, and the like. Namely, a search based on metadata still has difficulty in finding a meaningful file for a user. Thus, there is a need to easily find a desired file, especially meaningful to a user.